Due to their high quality printed output and reasonable cost, the market for ink jet printers is currently expanding. As the market's appetite for ink jet printers grows, so does its expectation of improved image quality. A goal of ink jet printer design is to achieve image quality approaching that of continuous tone images, such as photographs. One approach to achieving photo quality images is increasing the number of gray-scale levels that the ink jet printer can produce.
Ink jet printers form images on paper by ejecting ink droplets from nozzles in a print head. Heating elements in the print head heat the ink causing bubbles to form which force the ink from the nozzles. By printing pixels using combinations of ink droplets of multiple sizes, the number of gray-scale levels produced by an ink jet printer can be increased.
One approach to producing ink droplets of multiple sizes is to eject the droplets from nozzles of multiple sizes. However, using multiple nozzle sizes without a corresponding adjustment in heater resistor size is not energy efficient. Multiple-size droplets can be achieved in a more energy-efficient manner by adjusting the size of the heating elements in relation to the size of the ink droplets to be ejected from the nozzles.
However, varying heating element sizes in an ink jet print head can cause undesirable variations in the energy delivered to the ink. These variations in energy reduce the overall quality of the printed image.
Therefore, an ink jet print head is needed that is capable of printing ink droplets of multiple sizes without undesirable variations in the amount of energy delivered to the ink.